微管组装动力学。随溶液条件的变化。
Microtubule assembly kinetics. Changes with solution conditions.
作者信息
Barton J S, Vandivort D L, Heacock D H, Coffman J A, Trygg K A
机构信息
Department of Chemistry, Washburn University of Topeka, KS 66621.
出版信息
Biochem J. 1987 Nov 1;247(3):505-11. doi: 10.1042/bj2470505.
The assembly kinetics of microtubule protein are altered by ionic strength, temperature and Mg2+, but not by pH. High ionic strength (I0.2), low temperature (T less than 30 degrees C) and elevated Mg2+ (greater than or equal to 1.2 mM) induce a transition from biphasic to monophasic kinetics. Comparison of the activation energy obtained for the fast biphasic step at low ionic strength (I0.069) shows excellent agreement with the values obtained at high ionic strength, low temperature and elevated Mg2+. From this observation it can be implied that the tubulin-containing reactant of the fast biphasic event is also the species that elongates microtubules during monophasic assembly. Second-order rate constants for biphasic assembly are 3.82(+/- 0.72) x 10(7) M-1.s-1 and 5.19(+/- 1.25) x 10(6) M-1.s-1, and for monophasic assembly the rate constant is 2.12(+/- 0.56) x 10(7) M-1.s-1. The microtubule number concentration is constant during elongation of microtubules for biphasic and monophasic assembly.
微管蛋白的组装动力学受离子强度、温度和Mg2+影响，但不受pH值影响。高离子强度（I>0.2）、低温（T<30摄氏度）和升高的Mg2+（大于或等于1.2 mM）会导致动力学从双相转变为单相。对低离子强度（I<0.069）下快速双相步骤获得的活化能进行比较，结果显示与高离子强度、低温和升高的Mg2+条件下获得的值高度吻合。由此可以推断，快速双相事件中含微管蛋白的反应物也是单相组装过程中使微管延长的物质。双相组装的二级速率常数分别为3.82（±0.72）x 10(7) M-1.s-1和5.19（±1.25）x 10(6) M-1.s-1，单相组装的速率常数为2.12（±0.56）x 10(7) M-1.s-1。在双相和单相组装的微管延长过程中，微管数量浓度保持恒定。
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